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Horsepower from 305

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by TXsizeK5, Dec 17, 2001.

  1. TXsizeK5

    TXsizeK5 1/2 ton status

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    How much hp can would come from a bored and rebuilt with performance parts , heads, cam, etc. From a 305? Thanks

    6in 87' K5 w/ 35" BFG muds.
    305/Sm465/ NP208
    Kn, 4.56's.
    In desperate need of a rebuild.
    Next- Eaton mech locker... Flows.
     
  2. hammer

    hammer 1/2 ton status

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    I would and have done it put a 350 bottom end with 305 heads and you'll love it 300+ hp if thats what you want

    <font color=red>Let me at it I can break it</font color=red>
     
  3. HarryH3

    HarryH3 1 ton status Author

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    Less than you would get if you put all the same parts on a 350 to begin with. [​IMG] [​IMG]

    Seriously, find a 350 builder to start with. They aren't that expensive. $100-300 should find you a core to start with, plus you can still drive your truck while the 350's being rebuilt. [​IMG] Call around to the junkyards, watch the local papers, and even check with engine rebuilders in your area. Even consider buying a complete vehicle that has the engine you want (all the better if you happen to stumble across a 400 in an old truck or station wagon), then yank the engine and any other parts you want and send the carcass to the junkyark. You might as well start with more engine to begin with. [​IMG]

    That's my 2 cents, but then, I was looking for a 350 or 383 to put into my Suburban, when I ran across a deal on a 454. There IS no substitute for cubic inches! [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  4. Liberator

    Liberator 1/2 ton status

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    Tell me more about putting the 305 heads on a 350. I'm putting a 350 in my truck and taking out the 305. My 305 heads are still good. Just ordered a Comp cams 4x4 Extreme cam and a performer intake for the 350 that's going in. What is the advantage of 305 heads on a 350?

    Bo

    If it breaks, it wasn't good enough!
    http://coloradok5.com/gallery/liberator
     
  5. hammer

    hammer 1/2 ton status

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    Depending which heads you have I've put a 350 bottom end in a monte carlo with the original top end and the heads were 60 cc heads witch gave me slightly more copression and i't basicly a 305 still just larger pistions. The only thing you will run into that is a problem is the dipstick on the older motors where the dipstick is on the driver side and you run manifold exaust. If you do this run triple gaskets on the driver side and bend the dipstick between the motor and the exaust maifold. Yes it works I'm driving my camaro with a crate motor and can't afford the $600 special headers for the emmisions

    <font color=red>Let me at it I can break it</font color=red>
     
  6. Liberator

    Liberator 1/2 ton status

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    I guess my question is: Should I keep the original heads on the 350 or put the 305 heads on the 350?

    Bo

    If it breaks, it wasn't good enough!
    http://coloradok5.com/gallery/liberator
     
  7. TX Mudder

    TX Mudder 1/2 ton status

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    The 305 haeds have smaller conbustion chambers than the 350 heads.
    This will raise your CR substantially. Compression = more HP. As long as you don't mind buying 91 octane and maybe even an additive then go for it.
    For what it's worth, I would build a truck engine to run on 87 with a moderate CR. Your mileage is going to suck no matter what, so at least make it cheap gas.
    -- Mike

    <font color=blue> Married to a woman who understands the need for <font color=orange>Hugger Orange. [​IMG] <font color=blue>
     
  8. Stoopalini

    Stoopalini 1/2 ton status

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    I'm not sure on the '87 305 heads, but if they are the swirl port heads, then I wouldn't recommend putting them on a 350 block.
    These swirl port heads create a severe flow restriction, and will limit your HP.

    Just thought I would mention this .....

    Thomas.

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  9. txbartman

    txbartman 1/2 ton status

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    According to my manuals, the stock 305 in my 85 only produced 165 HP from the factory. I am guessing I am pulling probably only 100 or so of that these days. For the money you plan to invest in your 305, I would recommend going with a basic 350 crate. You can get one from My Jimmy with all her projects!
     

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